WORCESTER— A former police officer who sued the district attorney's office in an effort to collect a $100,000 reward offered in the Molly A. Bish case told a jury today the reward money was "an afterthought."

Timothy S. McGuigan of West Brookfield testified in Worcester Superior Court that his main motivation in launching an unofficial investigation into the disappearance of Ms. Bish, a 16-year-old who vanished from her lifeguard post at Comins Pond in Warren on June 27, 2000, was to bring her abductor to justice.

Mr. McGuigan, a former police officer in North Brookfield and Sturbridge, led investigators to Ms. Bish's bathing suit on a Palmer hillside in 2003. The discovery led authorities to the missing teen's remains, but no one has been charged in her death.

Mr. McGuigan, who said a hunter told him about seeing the bathing suit the previous fall, is trying to collect a $100,000 reward offered by the district attorney's office in the Bish case. He filed suit against District Attorney Joseph D. Early Jr. in 2009, after Mr. Early and his predecessor, John J. Conte refused to pay him the money.

Mr. Conte and Mr. Early, who are both on the witness list in the case, maintain that the reward money, donated by several private citizens, was intended for information leading to the arrest and conviction of Ms. Bish's killer.

In his opening statement to the jury Monday, Mr. McGuigan's lawyer, Leonidas Chakalos, referred to a poster that was distributed by the Polly Klaas Foundation, a nonprofit California corporation, offering the $100,000 reward "for information leading to Molly."

If the district attorney's office was in disagreement with the terms of the reward as stated on the posters, which were displayed in state police barracks and other public places, it should have had them removed from "the public domain," Mr. Chakalos told the jury.

Assistant Attorney General Helene Kazanjian, representing Mr. Early, said in her opening that posters and other forms of publicity authorized and distributed by the district attorney's office and state police clearly stated that the reward was being offered for information leading to the arrest and conviction of Ms. Bish's abductor.

The 47-year-old Mr. McGuigan, a father of three who now works as a truck driver, said he developed a strong interest in the disappearance of Ms. Bish while employed as a North Brookfield police officer in 2000 and later began conducting his own, unauthorized investigation when publicity about the case appeared to subside.

"You have to keep it going. You have to talk to people," Mr. McGuigan told the jury.

"I found Molly Bish. I found Molly Bish because I talked to a lot of people," he said.

"A reward was never a motivating factor...It was about bringing a child home," Mr. McGuigan said under direct examination by Mr. Chakalos.

"I found the point of origin where I knew Molly would be, her bathing suit," he said.

Mr. McGuigan testified that he had also had a strong interest in the case of another missing child, Holly Piirainen, and that at one time he was considering writing a book about the two cases.

"I was very much driven to bring these girls home," he said

Shown a series of posters and press releases from Mr. Conte's office concerning the reward for information leading to the arrest and conviction of Ms. Bish's abductor, Mr. McGuigan said he did not recall seeing them before applying for the reward money.